Systems and methods are disclosed for cumulative attribute forecasting using a probability density function of a current-to-future value ratio. Some method embodiments may comprise determining an unconditional probability density function for a ratio of a cumulative attribute's current value to an associated future value for the cumulative attribute, and determining an unconditional PDF for a future value of the cumulative attribute. The unconditional probability functions are combined with a current value of the cumulative attribute in a manner that yields a conditional probability density function for the future value. The conditional probability density function may then be used to determine forecasts such as a most likely future value, a mean value, a median value, a confidence interval for the future value, and a probability of achieving a future value within some specified range.